Method of producing rubber soles for boots and shoes



UNITED STATES PATENT onnron.

MYRON H. CLARK, 0F HASTINGS-ON-HUDSON, NEW YORK, ASSIGNOR TO BOSTON RUBBER SHOE COMPANY, A CORPORATION OF MASSACHUSETTS.

METHOD OF PRODUCING RUBBER SOLES FOR BOOTS AND Specification of Lettersl'atent.

Patented Oct. 14, 1919.

No Drawing. Continuation of application Serial No. 878,935, filed December 24, 1914. This application filed July 6, 1916. Serial No. 107,853.

To all whom it may concern:

Be it known that I, MYnoN H. QnARK, a citizen of the United States, res1d1ng at H astings-on-Hudson, county of Westchester,

State of New York, have invented certain new and useful Improvements in Methods of Producing Rubber Soles for Boots and Shoes, of which the following is a full, clear. and exact description.

This invention relates to a method of 'iroducin soles from vulcanizable lastics rubber compound and to vulcanize the sole Molds suitable ior this while in the mold. purpose are expensive and have to be replaced by other molds to meet the change in styles of footwear. The molding process furthermore is slow so that a comparatively small output of soles requires a large expenditure for the molds. The molded sole has the further disadvantage that a thin flash of rubber is formed on the periphery of the sole between the mold sections, which is not removed without considerable trouble.

In the manufacture of soles by my method, the rubber may be mixed with suitable compounds in the usual Way and when in proper condition it is subjected to the action of calender rolls to produce the desired sheet from which the soles are cut or stamped. There are many well known rubber compounds suitable for use in the manufacture of soles, and my application is not limited to any particular compound. For instance. in the publication entitled, The

, d/(mufacmre 0 Rubber. by Adolf Heil and Dr. Esch, edition of 1909, page 81, may be found compounds for soles containing among other ingredients, rubber gum, reclaimed rubber, carbon-black, litharge, Whiting, sulfur, barytes, etc. There are however, such numerous and well known compounds that nothing furth'er need be said here relating thereto.

In the manufacture of rubber soles for rubber boots or shoes wherein the soles are vulcanized to the uppers, the stock is sheetcd out substantially as above mentioned and the soles are cut from the sheet usually in a transverse direction thereof. The soles are often of varying thickness in the direction of their length, and to accomplish this the calender roll is composed of circumferential bands of correspondingly varying diameter. The sheet of stock issuing from such a calender will thus be composed of bands of vary ing thickness running longitudinally, thereby making it necessary to cut the soles so that their lengths will run transversely of the sheet of stock, in order to produce the desired variations in the thickness of the sole at the toe, instep, and heel portions thereof. The usual practice inhandling such stock is to permit the sheets to rest for'a suitable period of time after they have been formed by the calendering machine to permit them to shrink and'to assume permanent or normal conditions. The custom in most rubber factories is to permit the compounded rubber The stock is quite hot when it leaves the,

calender rolls and requires a comparatively long tune to sufliclently cool to assume nor mal or permanent conditions. hen the stock is cooled it .reaches the maximum slurinkagz'e which is mostly in a longitudinal direction. The sheet also thickens up to an amount corresponding to the degree of shrinkage. L

In carrying out my invention in its preferred manner,-I follow the foregoing procedure as it provides a ready means of more closely determining in advance the ultimate sizes which the soles will assume and gives more positive results. While the stock during its rest period has assumed a permanent condition in so far as the green sheet is" concerned. it is usual however. that during the vulcanizing pro cess ial re sole in its transformation from the green to the vulcanized idinally and greater i V f 1 this regard resembling very much ..ture of a structure having a grain er running longi .linally.

' out of my me d the soles have .n ushally cut transversely of the sheet, is to si ty, the length of the sole runs y of the sheet so that the sole pos strength transvcrsel y and ility longitu clinally These calencered sole advantages not molded sole. rolls give the sole an irreguin thiclmcss, the dili'crenccs in separated by wavy lines runely of the solo. The irregumanifest adjacent these e the sole the appearance might be termed a piltcd s, the uneven portions being somewhat of flakes imperfectly adherbodv of the sole and sometimes g lhercfrom so that diiiima in of; lame cases cc. experienced in W cen'icnting the sole to an adjoining such as the welt sole of the shoe. 'pplying the cut or calcndercd solos berboots and shoes, the usual practice been to attach the sole to the shoe in its r unvulcanized state and than to sub entire article to the :ulcauiziug iis method, however, is not well shoes or boots having leather he leather will not withstand ls somewhat dependent upon the nature the ingredients forming the rubber com pound, and the temperature at which the calender rolls are run, I believe the pitting is primarily due to an alternate pulling and lu the l adapted to solos and give ness, have a partial slipping act-ion olbthe rubber surface so that the drawing of the rubber from the bank is not uniform, which results 1n producing the uneven flaky or p1tted surface commonly deslgnated 1n rubber factories a fish-scale surface. I have found that if the rolls can procure a firmer grip into the rubber this unevenness may be regulated as desired or reduced to a minimum. In carrying out my invention, there fore, I may when desired, provide one or both of the calender rolls with a gripping surface, preferably by knurling the surface, although it is obvious that many other engraved designs may be resorted to.

Where smooth rolls are exclusively used, the surface of the stockis quite irregular, the irregularity depending somewhat upon the nature of the compound used, as has already been mentioned. Such soles may be saleable in certain sections and'adapted for certain uses, such as lumbermens boots and for other rough usages Where anattractive appearance is not sought. Furthermore, where only one of the rolls is smooth and the other knurled as described above there will obviously be two surfaces formed, the smooth roll producing the pitted surface and the knurled roll the engraved surface. The knurled roll will however, influence to some degree the action of the smooth roll, so that the pitted surface will not be so pronounced. \Vhcre both rolls are knurled both sides of the sole will present an engraved surface, although usually the wavy or fishscale appearance is in evidence in combination with the knurled surface, but it is reduccd to a minimum as above mentioned.

\Vhile the knurled appearance presents a surface more attractive for high class or dressy footwear, my invention is obviously in its broad aspect not limited to such a surface, but in its broadest phase comprises a vulcanized sole having the natural calendercd surface, the words natural calen- (lei-ed being used in the sense that the vulcauizing process is so carried out that the finally vulcanized sole will not have lost the surface cluu'zu-leristics which the calender rolls have imparted to it regardless of what those characteristics may be.

in accordance with an important feature of my invention, I provide a sole, the surchine; that is, a sole having a natural surface. Prior to my invent-ion, so far as I am aware, when vulcanized apart from the shoe, rubber soles have invariably been} vulcanized in a mold, the n'iembers of which contact with the surface, and impart to the sole unnatural or polished surfaces substantially dcvoid of pits or irregularities or bthei configurations produced during the' calendaring process. In .order to preserve the surface particles of the material constituting the tion upon shelves.

sole, being unrestrained, do actually, during vulcanization, flow or move about and accommodate themselves to each other in such a manner as to result in producing a superior article. The sole therefore has a surface, the particles of which are self-distributed and the particles of the sole are distributed in accordance with the normal or substantially free or unrestrained flow thereof. This not only preserves the natural, calendered surface of the sole, but obtains such a distribution of particles throughout the sole as to improve the product.

A sole' made by the use of knurled rolls is characterized by having a substantially uniformly even surface in the sense that it does not possess the irregular haphazard unevenness of the sole made by the use of smooth rolls. WVhen it is desired to provide a sole having an entirely smooth surface, the knurls or other design may be removed bybutfing orotherwise treating the surface. In such case, the design may be made so small that it can be removed with but little trouble, whereas, to buff down the surface of a sole made by the use of smooth rolls would require considerable time and trouble and represent considerable loss of rubber, inasmuch as the bufling is performed after the sole has been vulcanized.

In the practice of my invention in its most preferred manner, the rubber is compounded with the desired ingredients in the usual manner upon mixing rolls. It is then formed into sheets by passing it between calender rolls maintained at suitable temperatures and engraved or not, as desired.

The sheeted rubber is then permitted to rest in the usual manner, and is finally cut or stamped transversely to form the soles which are placed in an unconfined condi- These are placed in a vulcanizer and a fluid pressure, preferably of carbon dioxid gas, and heat applied to effect the vulcanization. The soles thus formed are homogeneous throughout and posses; greater strength transversely and greater flexibility longitudinally, and where engraved rolls are used, have a regularly even surface or surfaces which are the counterpart of the design upon the'roll or rolls.

lVhile I prefer to cut the sole transversely from a single sheet, it may be built of any desired number of plies of the green stock, the grain of the various plies running in the same or in different directions in ny desired manner, the several plies being taken from the same or different grades of stock. lVhere the soles are cut transversely of the sheet the calcndered rolls may be varied in diameter at different portions to provide greater thickness of stock at any desired parts of the sole, as for instance at the toe or heel portions as is the usual practlce in such articles. The rubber stock may be plied together in the sheet form or the several sheets may be first cut to form the laminations and these finally superimposed to form the sole. In either case the several plies are preferably brought into intimate association by means of pressure as by rolls or presses.

Having thus described my invention, what I claim and desire to protect by Letters Patent is:

1. The process of producing rubber soles which comprises forming the stock into sheets, permitting the sheet to remain in a quiescent condition until it assumes a substantially normal or permanent state, cutting therefrom sole blanks with their length corresponding to the transverse direction of said shefits, and thereafter vulcanizing said blanks while in a wholly free, unrestrained and unattached condition, whereby the shrinkage is thrown wholly into the length of the sole and whereby flow and intermovement of the n'iatcrial during vulcanization is effected.

2. The process of producing rubber soles which comprises forming the stock into sheets, permitting the sheet to remain in a quiescent condition until it assun. s a substantially normal or permanent state, form ing the sole from said sheet, and thereafter vulcanizing it in a wholly free, unrestrained and unattached condition.

3. That process of producing rubber soles which comprises forming the sole blank of rubber containing material and thereafter vulcanizing it in a wholly free, unrestrained and unattached condition.

4. A method for forming soles from rubber compound which consists in sheeting a mass of the unvulcanizcd compound by subjecting it to the action. of rolls, cutting the sheet to form soles, placing the soles in an unattached condition in a vulcanizing chamber, and thensubmitting the soles in said chamber to pressure and heat by means of a heated fluid and maintaining' the heat for a time sufficient to vulcanize the soles.

A method for forming soles from rubber compound which consists in sheeting a mass of the unvulcanized compound by subjecting it to the rolling action of an engraved surface, cutting the sheet to form soles, placing the soles in an unattached condition in a vuleanizing chamber. and then submitting the soles in said chamber to presill) sure and heat by means of a heated fluid and maintaining the heat for a time sufficient to vulcanize the soles.

6. A method for forming soles from rubber compound which consists in sheetinga mass of the unvulcanized compound by subjecting it to the action of engraved rolls, cutting. the sheet to formsoles, placing the soles in an unattached condition in a vulcanizing chamber, then sulnnitting the soles in said chamber to pressure and heat by means of a heated fluid and maintaining the heat for a time sufficient to vulcanize the soles,

and finally removing the engraved surfaces formed in the soles to produce a smooth surface.

7. A method for forming soles from rubber compound which consists in sheeting a mass of the unvulcanized compound by subjecting it to the action of rolls, cutting the sheet to form laminations for soles, assembling the laminations in superposed relation to form the soles, subjecting the soles to a compacting pressure and placing them in an unattached condition in a vulcanizing chamber. and While in said chamber, submitting them to pressure and heat by means of a heated fluid and maintaining the heat for a time suflicient to vulcanize the soles.

8. A method for forming soles from rubber compound which consists in sheeting a mass of the unvulcanized compound by subjecting it to the action of rolls, cutting lamimasses of the unvulcanized rubber compound of different grades, superimposing and cutting laminations to form soles and placing them in an unattached condition in a vuleanizing chamber, and While in said chamber, submitting them to pressure and heat by means of a heated fluid and maintaining the heat for a time suflicient to vulcanize the soles.

10. That process of producing rubber soles which comprises forming the stock into sheets, cutting therefrom sole blanks'with their length corresponding to the transverse direction of said sheets, and thereafter vulcanizing said blanks while in a wholly free, unrestrained and unattached condition, whereby flow and intermovement of the material during vulcanization is effected.

Signed at New York, New York, this 3rd day of July, 1916.

MYRON H. CLARK. 

